The invention relates to a precision-mechanical positioning device for positioning a second component relative to a first component in any of the directions perpendicular to a combined straight line between the components, the positioning device comprising: a stationary basic member included in the first component and having a first plane sliding surface perpendicular to the said straight line a support member included in the second component and having a second plane sliding surface; the support member being connected to the basic member such that the second sliding surface bears against the first sliding surface, forming a pair of sliding surfaces; and the support member comprising at least two holes transverse to the plane of he pair of sliding surfaces, locking means comprising shanks extending through these holes to the basic member, the thickness of the shanks in a direction transverse to the hole length being smaller than the hole diameter, and clamping means for pressing the support member into immobile contact with the basic member after the positioning has been performed. The invention relates in particular to the positioning of an optical element, such as a set of lenses, relative to a second optical component, such as a laser or any other source of radiation, and particularly in a direction perpendicular to the direction of motion of the radiation.
The inventor's previous Patent Application, WO 95/32508, describes a precision-mechanical positioning device for positioning a second component relative to a first component parallel with a straight line between the components, which is typically the optical axis of these, in other words, the positioning takes places in the axial direction. The structure described in this publication allows extremely accurate axial adjustment, however, when a set of lenses is to be positioned for instance relative to an emitting laser or the like, adjustment transverse to the optical axis will be required in addition to the adjustment parallel to the optical axis as described in this publication, for the optical axis of the set of lenses to be positioned at the right: location in the beam of rays.
Adjusting devices for moving an element in a specific plane, i.e. perpendicular to any straight line, such as an optical axis, have been accomplished with the use of, for instance, micrometric screws operating in mutually perpendicular directions parallel to the plane, enabling adjustment parallel with the plane to be obtained with adequate accuracy. Nevertheless, such a design using micrometric screws will be extremely complex, because one has to take care that the use of the one micrometric screw does not interfere with the positioning already performed by means of the other micrometric screw. Due to this complex design, the structures still frequently include non-controllable plays, which in reality result in a very awkward and slow positioning operation. In addition, such complex structures which comprise several components requiring high precision are very expensive.
The prospectus THORLABS INC., USA, May 1995, describes on pages 24 to 25 slip plate positioner, which in terms of the description in the prospectus, is designed to provide for instance coarse X, Y positioning of optical components. The structure comprises a stationary basic member having a protruding planar dry sliding surface, and a support member having a second planar dry sliding surface, the surfaces being maintained slightly pressed against each other by means of two helical springs subjected to tensile stresses. This structure yields an unlubricated pair of sliding surfaces, the outer support member being manually movable relative to the stationary basic member in a direction parallel to this plane. In addition, the device comprises two locking screws, whose heads get into direct contact with the outer surface of the support member during the tightening of the screws, and which extend through holes in the support member to the basic member, which is provided with counter-threads. The diameters of the helical screws are smaller than the diameter of their positioning holes in the support member, and similarly, the thickness of the shanks of the locking screws is smaller than the diameter of their through-holes in the support member, and further, the diameter of the pins passing through the entire structure is smaller than the diameter of their through-holes in the support member. This arrangement enables the support member to be manually shifted in the plane of the pair of sliding surfaces within the range allowed by the plays .+-.1 mm, and to be locked into position after adjustment. The optical. components are fastened to the support member by some means not illustrated here. In practical testing, the structure described has at least the following shortcomings. When the support member is to be shifted in some direction, it is difficult to get moving, however, when it does move, its movement is usually excessive in practice, and in turn, when the approximately correct position is to be resumed, the support member moves too far again, not allowing the centration desired to be approached under control, but instead, there will be a nearly infinite number of attempts in various directions, one of which might eventually bring the support member close to its correct position. The problem described above is probably due to the commonly known physical fact that the filly developed static friction prevailing between two surfaces is greater than the dynamic friction. Should the support member after all be centred in its correct position with adequate accuracy in the structure described in the prospectus, the positioning of the support member would anyhow be dislocated again when the locking screws are tightened. Thus, it is quite impossible to achieve sufficient precision with the positioner mentioned in the prospectus for instance in the positioning of a set of lenses relative to a laser. In practice, the optimal adjustment precision obtained with some degree of reliability by means of the structure in the prospectus has proved to be of the order of 0.1 mm, which is not at all sufficient for the positioning of a set of lenses relative to a laser, and for other optical applications as well. For this reason it is understandable that the prospectus stresses explicitly that it is merely designed to provide coarse positioning, without aiming to provide the positioning accuracy finally desired.